Anyone know rocker arm ratio?

[HondaRaceReady]

I can't find it in the service manual. What I mean by rocker arm ratio is how far do the exhaust valves actually open when the cam lobe is at full lift on the rocker arm. Do they open the entire amount of lobe height (minus valve clearance)? For example, I know HD twin cam engines use a rocker arm ratio of 1.65:1 meaning for every 1" of cam lobe height the valve will open 1.65". I know my numbers are exagerated. Im trying to figure out exhaust valve lift and Im guessing the ratio is 1:1 just by looking at the lobe height but I want to be sure.

[DnB_racing]

Originally posted by HondaRaceReady
I can't find it in the service manual. What I mean by rocker arm ratio is how far do the exhaust valves actually open when the cam lobe is at full lift on the rocker arm. Do they open the entire amount of lobe height (minus valve clearance)? For example, I know HD twin cam engines use a rocker arm ratio of 1.65:1 meaning for every 1" of cam lobe height the valve will open 1.65". I know my numbers are exagerated. Im trying to figure out exhaust valve lift and Im guessing the ratio is 1:1 just by looking at the lobe height but I want to be sure. the total amount of lift depends on the lift of the cam, here is a little info you might find useful,,, if you have a cam that measures .350 of lift, this is the total amount that the bucket will be pushed if you if you dial indicated it


http://www.google.com/url?sa=t&source=web&cd=1&sqi=2&ved=0CB0QFjAA&url=http%3A%2F%2Fwww.trx450r.org%2Fforum%2F93-engine%2F136727-trx450r-cam-guide.html&ei=QB-eTtjXFcz3sgaAucW1CQ&usg=AFQjCNFGTE1KZtLkniWi6p_uzMsUoZbh4A&sig2=KG0c-Xls5HvCcUWVNbcnJQ

[HondaRaceReady]

the total amount of lift depends on the lift of the cam, here is a little info you might find useful,,, if you have a cam that measures .350 of lift, this is the total amount that the bucket will be pushed if you if you dial indicated it

Thanks, I guess? I already know that. I was asking about the exhaust valves though. Im sure you know the cam lobes dont push directly on the exhaust valves and thats where the ratio of the rocker arms come into effect. If I wasnt 850 miles away from my engine I would have just measured the lift with a dial indicator like you said. I cant do that though and the only information I have to figure out exhaust valve lift is the exhaust lobe height which is 34.214-34.454. Just because thats the lobe height doesn't necessarily mean thats the lift.
Cam lift x rocker ratio = valve lift

Im missing one variable in this equation

[DnB_racing]

Originally posted by HondaRaceReady
Thanks, I guess? I already know that. I was asking about the exhaust valves though. Im sure you know the cam lobes dont push directly on the exhaust valves and thats where the ratio of the rocker arms come into effect. If I wasnt 850 miles away from my engine I would have just measured the lift with a dial indicator like you said. I cant do that though and the only information I have to figure out exhaust valve lift is the exhaust lobe height which is 34.214-34.454. Just because thats the lobe height doesn't necessarily mean thats the lift.
Cam lift x rocker ratio = valve lift

Im missing one variable in this equation well if you think about it the rocker is more of a roller following the lobe so I would have to say its a 1:1 ratio

the web cam I just installed advertises a .350 lift and it does dial to exactly that at full lift from no lash

[HondaRaceReady]

Cool thanks for your help.

[440ex. ehhh!!]

Originally posted by HondaRaceReady
Thanks, I guess? I already know that. I was asking about the exhaust valves though. Im sure you know the cam lobes dont push directly on the exhaust valves and thats where the ratio of the rocker arms come into effect. If I wasnt 850 miles away from my engine I would have just measured the lift with a dial indicator like you said. I cant do that though and the only information I have to figure out exhaust valve lift is the exhaust lobe height which is 34.214-34.454. Just because thats the lobe height doesn't necessarily mean thats the lift.
Cam lift x rocker ratio = valve lift

Im missing one variable in this equation

If you are missing one variable, then just rearrange the equation...its simple math. since you dont have the rocker ratio, it would be....rocker ratio=valve lift / cam lift
Theres the answer.

Josh